Why was it created?

In order to enhance competition, the Formula SAE rules require each competing team to include a device in the intake system that limits the amount of air entering the engine. The smallest internal restrictor cross section must not have a width of greater than 0.787" (20 mm) in any direction, the openings must end on both sides in a 0.25” straight section with an internal diameter of 1.5”, the maximum restrictor length must be 10” and the maximum restrictor diameter must be 2.5”.

Initial Design & Rationale

Started with a 2d sketch, revolved around the x axis
10 inches long, inlet/outlet with circumferences of 1.5 inches
20 mm circumference Choke positioned more towards the inlet side, 3.75 inches
- Giving the air more distance to travel on the outlet side will allow for it to accelerate after being pushed through the choke
- It is most ideal to increase the diameter as soon as possible after the choke because when the diameter is small, the pressure drop is large
- Giving the air more room for travel before the outlet allows for it to recover from the high pressure it will experience at the choke, so the choke must be closer to the inlet side
- This design produced a mass flow rate of 0.0388 kg/s

Refinement & Rationale

I identified two main factors to change: location of choke & inlet shape, making a curve on the inlet side allows for air to funnel into the choke. This is because air is able to move faster on a curved line than on a straight line due to its fluid like behavior. The outlet side was kept straight instead of curved in order to increase the diameter as soon as possible after the choke.

Final Results

The final iteration produced a mass flow rate of 0.0421 kg/s, along with the following pressure cut plot. Solidworks was used to create 3D models of the restrictor, and Solidworks Flow Simulation was used to run CFD analysis on the models.

Air Restrictor